Operators have been stimulated to reduce fuel consumption by displaying indexes for reducing fuel consumption on a display means in a work mechanism such as a shovel (see, for example, Patent Document 1).
In the shovel disclosed in Patent Document 1, fuel consumption per unit time or fuel consumption per work amount is measured during the work, and the difference between the measured fuel consumption per unit time and a target value of fuel consumption per unit time that has been set, or the difference between the measured fuel consumption per work amount and a target value of fuel consumption per work amount that has been set is displayed on a display means. Further, in this shovel, when the measured fuel consumption per unit time is larger than the target value of fuel consumption per unit time, or when the measured fuel consumption per work amount is larger than the target value of fuel consumption per work amount, a guidance instructing to improve fuel efficiency is displayed on the display means.
However, with the technique disclosed in Patent Document 1, the display for improving fuel efficiency is performed on the display means during the work and therefore the concentration of operator is divided between the crane work and the recognition of the display contents. As a result, the operator cannot sufficiently maintain the accuracy of crane work and also cannot sufficiently review the work contents for improving fuel efficiency. Further, where attention is called only to the improvement of fuel efficiency, without demonstrating the work results, as in the technique disclosed in Patent Document 1, the total cost reduction is impossible to achieve. Thus, even if fuel consumption is low, where a very small work has been performed, the actual cost of this work can be high.    Patent Document 1: Japanese Patent Application Publication No. 2005-98988.